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Shedding Light on Fluro Myths

In my one-man quest to improve my office’s energy efficiency, I turn the air-conditioning on warmer, set timers, and switch appliances (e.g. printers) off when no-one is using them. One day of my office-mates – from a different division, it should be noted – queried my behaviour, claiming it would take far more energy to restart/turn on appliances and lightbulbs than I was saving by turning them off for a few hours. In fact, he claimed to have read that if you turn fluorescent lightbulbs off more than once a day, you can’t leave them off long enough in those 24 hours to save more energy than you’ll spend turning them on again.


The amount of energy required to start fluorescent lightbulbs is far, far less than what’s needed to run them. The energy required to start a fluoro light is, in fact, equal to about 5 seconds of running time, so can turn them off and on thousands of times each day without wasting power. (If you include the shortening effects on their lifespan, the rule of thumb for efficient use of fluoro lights is to turn them off if you won’t need them for >15 minutes.)

So say the US Department of Energy, Scientific American, and the Lighting Design Lab.

I’ve also found several university energy policies and this government website that encourage turning network printers/copiers off overnight and when not needed to copy at a moment’s notice, e.g.

Figures I’ve seen for computers suggest it’s more efficient to turn them off for 20 minutes than to leave them idle, so even with generous assumptions for printer/copiers I doubt you could justify leaving them on for more than an hour without use.

To sum up: poppycock, balderdash, tosh, and piffle. Turn everything off when you’re not using it. Make it the rule, and then make exceptions when you find you need to, not the other way around.

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